Powder compacts of alumina-pillared fluorine micas having different particle sizes were fired at various temperatures in the range of 500-800 degrees C. Sintered bodies of the alumina-pillared micas were obtained at 500-700 degrees C with retaining their pillared structure. The pillared structure collapsed at 800 degrees C, losing microporous characters. Specific surface area and micropore volume of the sintered bodies obtained from coarse particles are larger than those obtained from fine particles. Thermal durability of the pillared structure depends on the particle size of alumina-pillared fluorine micas, especially on the c-dimension of the host mica crystals; thermal durability of the sintered bodies obtained from coarse particles is higher than that from fine particles. The sintered bodies are machinable due to the interlocking microstructure of the flaky mica crystals.